Pressure atomizing burners or liquid spray heads have been heretofore used to atomize or spray liquid in the various fields of art as mentioned above. The term "liquid" herein used is intended to mean not only liquid but also various liquid materials such as solution, suspension and the like. Injection nozzles used with such spray burners or liquid atomizers relied for atomizing the liquid on the shearing action between the liquid as discharged through the nozzles and the ambient air (atmospheric air). Thus, increased pressure under which liquid was supplied was required to achieve atomization of the liquid, resulting in requiring complicated and large-sized liquid supplying means such as pumps and piping.
Furthermore, regulation of the flow rate of injection was effected either by varying the pressure under which to deliver supply liquid or by varying the area of the nozzle discharge opening. However, the former method provided poor atomization at a low flow rate (low pressure), as a remedy for which air or steam was additionally used on medium or large-sized boilers to aid in atomization of liquid, requiring more and more complicated and enlarged apparatus. On the other hand, the latter method required an extremely intricate construction of nozzle which was troublesome to control and maintain.
In order to overcome the drawbacks to such conventional injection nozzles, attempts have been made to impart ultrasonic waves to liquid material as it is injected out through the jet of the injection nozzle under pressure.
However, the conventional ultrasonic liquid injecting nozzle had so small capacity for spraying that it was unsuitable for use as such injection nozzle as described above which required a large amount of atomized liquid.
As a result of extensive researches and experiments conducted on the ultrasonic liquid atomizing mechansim and the configuration of the ultrasonic vibrating element in an attempt to accomplish atomization of a large amount of liquid, the present inventors have discovered that large quantity of liquid may be atomized by providing an ultrasonic vibrating element formed at its end with an edged portion along which liquid may be delivered in a film form, and have proposed an ultrasonic injection method and injection nozzle based on said concept as disclosed in Japanese Patent Application No. 59-77572.
The present invention relates to improvements on the ultrasonic injection nozzle of the type according to the invention of the aforesaid earlier patent application, and particularly to improvements on the vibrating element for use with such ultrasonic injection nozzle.